近年来，以美国为首的西方国家对华发动的舆论攻势使得中国一直面临着巨大的国际舆论压力，主流媒体如何掌握主动权与话语权、设置有利于中国的国际舆论议题成为中国国际传播工作的重中之重。但学界对如何从实证角度考察中国主流媒体在国际舆论场上的议程设置能力关注甚少。本研究引入议程设置理论来讨论这一问题，并试图丰富和补充以往关于社交媒体上议程设置效果研究的证据。以往基于社交媒体数据的部分研究挑战了传统议程设置理论认为媒体议程设置了公众议程的核心假设，而国内在议程设置理论的相关研究中很少以社交媒体的大样本数据作为研究对象。本研究以推特和微博上关于中兴事件和华为事件的80万条数据作为样本，在对社交媒体上媒体议程和公众议程进行梳理的基础上，进一步检验了传统议程设置理论和网络议程设置理论在推特和微博上的适用性，并从实证角度考察了中国主流媒体的跨国议程设置能力。在对推特和微博上媒体议程和公众议程的描述中，本研究发现，中兴事件和华为事件中微博和推特上都呈现出媒体议程与公众议程趋同的特征，政策变动是影响媒体报道数量和公众注意力的直接因素。推特上媒体和公众更倾向于关注政治与政策议题，尤其是推特上的公众在中兴事件中对美国政府的政策和领导人信任问题进行了大量的关注和讨论；而微博上的媒体和公众更倾向于关注芯片与自主产权核心技术、国家战略与发展等议题，呈现出明显的反思性和爱国情感。在对社交媒体上议程设置效果的检验中，本研究发现了微博和推特上都存在明显的媒体议程和公众议程互相设置的效果，媒体议程和公众议程在不同议题上呈现出复杂的动态交互过程。研究发现，媒体在技术议题、政治和政策等专业性较强、信息获取难度较大的议题上仍然对公众有明显的单向议程设置效果；政治因素对议程设置过程产生了巨大影响，特朗普“推特治国”的风格使得公众完全可能绕过媒体来形成议程。此外，本研究利用网络议程设置理论的研究方法发现了推特平台上媒体为不同议题构建的关系网络影响了公众认知网络的构建过程。相对于美国媒体和其他国家媒体来说，尽管中国媒体在部分议题上拥有主动权和发言权，但是总体来看中国媒体的跨国议程设置能力相对较弱，这意味着中国主流媒体在推特上的影响力和话语权较为有限，甚至在中兴事件中存在着“自说自话”的叙事困境。这启示中国主流媒体在国际传播工作中要充分发挥自身优势，主动设置有利于中国的国际舆论议题。

In recent years, China has been facing enormous pressure from international public opinion due to public opinion attacks from Western countries led by the United states. The focus of international communication is how Chinese mainstream media can set up international public opinion issues that are benefical to China. However, there are few studies have examined the ability of Chinese mainstream media to set issues in the field of international public opinion from an empirical perspective. This study uses agenda-setting theory to discuss the issue and attempt to enrich the evidence from previous research on agenda-setting on socail media.Some previous studies based on social media data have challenged the assumption of traditional agenda-setting theory that media agenda sets the public agenda, but domestic research on agenda-setting theory rarely used social media as a sample. This study uses 800,000 pieces of data about “ZTE incident” and “Huawei incident” on Weibo and Twitter as samples to describe the media agenda and public agenda on socail media. In addition, this paper examines the applicability of traditional agenda-setting theory and network agenda-setting theory on social media. On this basis, the study examines the Chinese mainstream media’s ability to set the agenda for foreign publics from an emprical perspective.In the description of the media agenda and public agenda on Weibo and Twitter, this study found that the public agenda on Weibo and Twitter tended to be consistent with the media agenda in the ZTE incident and the Huawei incident. And the policy was a direct factor that affected media and public attention. The media and the public on Twitter paid more attention to political and politic issues, especially the public on Twitter had paid a lot of attention and discussion on the US government’s policies and whether Trump was corrupt in the ZTE incident. However, the media and public on Weibo paid more attention to issues such as core technology of independent property rights and national strategy and development, showing obvious reflection and patriotic sentiment.In the test of the effect of agenda-setting on social media, this study found that there was an obvious effect of mutual setting of the media agenda and public agenda on Weibo and Twitter. And the media agenda and public agenda presented a complex dynamic interaction process on different issues. But the media still had an obvious agenda-setting effect on the public on some issues that are highly specialized and difficult to obtain information, such as technology, politics and policy. The political factors had a huge influence on the agenda-setting process. Trump’s habit of tweeting his own policy views makes it possible for the public to bypass the media to form their agenda. In addition, this study used the research method of network agenda-setting theory to find that the relationship between different issues constructed by the media influence the process by which the public builds relationship on these issues.Compared with the US media and other national medias, although the Chinese media have the initiative and the power to speak on some issues, in general the ability of the Chinese media to set agendas for foreign publics was relatively weak, which means that the Chinese mainstream media had limited influence and power to speak on the Twitter. And there was a narrative dilemma of “talking to oneself” in the ZTE incident. This suggests that Chinese mainstream media should take advantage of their own advantages in international communication, actively set the agenda that are beneficial to our country, and targetedly solve the passive situation in international communication.